Spark-plug.



A. SCHMIDT.

SPARK PLUG.

APPLICATION FILED JAN. B, 1916.

Patented Mar. 20, 1917.

@31 WW mm imam STATES A PATENT omen.

ALBERT SCHMIDT, 0F FLINT, MICHIGAN, ASSIGNOR TO CHAMPION IGNITION COMPANY, OF FLINT, MICHIGAN, A CORPORATION OF MICHIGAN.

SPARK-PLUG,

m Specification of Letters Patent.

Patented Mar. 20, 11911 7..

' Application filed January 8, 1916. Serial No. 70,906.

To all whom it may concern:

Be it known that I, ALBERT SCHMIDT, a citizen of the Republic of France, residing at Flint, in the county of Genesee and State of'Michigan, have invented certain new and useful Improvements in Spark-Plugs, of which the following is a specification, reference being had therein to the accompanying drawings.

The invention relates has for its object the protection of the insulator from fouling.

In the drawings:

Figure 1 is a longitudinal section through the plug; and

Fig. 2 is a similar View cation.

In the use of spark plugs in explosion enshowing a modifigines using low-grade fuels great difficulty is experienced in the sootin of the surface of the insulators so as to d estroy their dielectric property. The sooting is caused by the imperfect combustion of the gas in contact with the insulator surface, and on account of the high pressure incident to the explosion the gas is forced against all portions' of the structure. With the present in- .vention I have overcome this difliculty by as a wrapping of mica to prevent placing the insulator in a'chamber in communication with the gas space of the explosion chamber but separated therefrom by means barring the passage. of the flame. Thus, while the gases are permitted to pass back and forth between the insulator chamber and the explosion chamber the gas-in the former is not ignited and therefore-Will not produce a carbon deposit.

In detail, A is the metallic casing of the plug and B is the insulator seated therein and surrounding the electrode C. D is an extension of the casing A which surrounds an inwardly-projecting portion of the electrode forming a tubular passage therebetween of relatively small area. The surrounding tubular portion of this casing is preferably lined with an insulator E, such short circuiting, while the outer end F thereof forms the grounded electrode.

With the construction as described, when orced through the tubular passage sur- 5 rounding the electrode into the chamber C to spark plugs and termediate adjacent bafiles chamber of considerable volume.

forth willfree the passage from any fouling of soot or other material which might short circuit the electrodes. When explosion oc curs, the gases will be forced inward as before stated, but the absorption of heat through the walls of the tube will lower the temperature sufficiently to prevent the passage of the flame. Consequently the gas within the chamberG is not ignited and cannot foul the surface of the insulator.

In Fig. 2 a modified construction is shown, in whic the electrode C issurrounded by a series of baflies H extending inward from the wall of the casing A. The space between the electrode and the baflies is slight, but inis an expanded Thus the gas passing into and out from the chamber surrounding the insulator is checked in its velocity by the bafiles H which further guards against the possibility of passage of flame. The baffles H may be insulated from the casing by interposed insulation I, and a grounded electrode J extends from the casing into proximity to the end of the electrode'C.

To successfully bar the passage of flame is is essential that the length of the gas passage into the insulator inclosing chamber should have a length considerably greater than its diameter. This is secured by the relatively long tube, as'shown in Fig. 1, and b the series of baffles, as shown in Fig. 2. A so as above stated the latter construction forms an additional check in the throttling effect of the chambers between the baffles.

What I claim as my invention is 1. In a spark plug, the combination of an insulator, a casing surrounding said insulator and forming an inclosing gas chamber with a restricted passage communicating with the explosion chamber, an insulator lining to said restricted passage, and an electrode passing through said insulator and rethrough said insulator and said tube free ing a flame-guard, and having a passage from the Walls of the latter, the outer end through which the projecting electrode exof said tube forming the cooperating electends restricted and insulated to form hightrode. velocity gas currents therethrough upon Va- 5 8. In a spark plug, the COIl'lbll'lfttlOIl With riations inpressure in, the explosion chamber. an insulator and an electrode passing there- In testimony whereof I aifix my signature.

through and projecting therebey'ond, of a casing surrounding said insulator and form- ALBERT SCHMIDT. 

